diff --git a/src/controller/main.c b/src/controller/main.c
index 88a21fca..770b9757 100644
--- a/src/controller/main.c
+++ b/src/controller/main.c
@@ -70,9 +70,13 @@ static error_t parse_opt(int key, char* arg, struct argp_state* state)
         break;
     case OPT_CONF_KEEP_N:
         arguments->conf_keep_n = atoi(arg);
+        if (arguments->conf_keep_n < 1)
+            argp_error(state, "--conf-keep-n must be >= 1 (got: %s)", arg);
         break;
     case OPT_CONF_STALE_TIMEOUT:
         arguments->conf_stale_timeout = atol(arg);
+        if (arguments->conf_stale_timeout < 0)
+            argp_error(state, "--conf-stale-timeout must be >= 0 (got: %s)", arg);
         break;
     default:
         return ARGP_ERR_UNKNOWN;